Conventionally, a head-up display device (hereinafter, an HUD device) that realizes display of a virtual image of a display image by diffusing laser light, which carries the display image, using a screen member so as to introduce the laser light to a projection surface has been known.
For example, an HUD device disclosed in patent literature 1 diffuses laser light, which enters a screen member after being projected from a projector, using a plurality of optical elements which are arrayed in the form of a grating. The laser light thus diffused and projected onto a projection surface is discerned as a virtual image of a display image by a discerning person inside a moving entity.